After defeating her sister Venus (6-4, 6-4), in the finals during the 2017 Australian Open, Serena Williams became the only player -- man or woman -- to win 23 Grand Slam singles titles in the Open Era. Williams passed Steffi Graff who finished her career with 22 Grand Slam singles titles. Fun fact: Serena was 2 months pregnant when she claimed that elusive 23rd Grand Slam title at this years Australian Open.